1. Field of the Invention
The present invention relates to a fuel supply apparatus for an engine, for controlling a fuel pump so that a fuel supply pressure applied to a fuel injection valve approaches a target value, and a control method thereof.
2. Description of the Related Art
Japanese Patent National Publication of Translated Version No. 2000-511992 discloses that, in a fuel supply apparatus for operating a fuel pump based on both a fuel pressure detected by a pressure sensor and a reference pressure, in the case where an abnormality in the pressure sensor is detected, the fuel pump is operated based on a required engine fuel amount and an engine rotating speed.
When the abnormality in the pressure sensor is detected, a discharge amount required for the fuel pump after an occurrence of the sensor abnormality depends on whether or not a pressure inside a fuel piping is boosted to the vicinity of a target pressure.
However, in the case where the fuel pump is operated based on both the required engine fuel amount and the engine rotating speed as in the conventional technology, since the fuel pump is operated so as to compensate for the fuel consumption, there is a problem in that the pressure inside the fuel piping cannot be boosted, resulting in the significant discrepancy between an actual fuel pressure and the target pressure.
Namely, in the fuel pump controlling operation based on both the required engine fuel amount and the engine rotating speed, although the fuel pressure can be held constant, the fuel pressure cannot be changed and consequently, sometimes, the fuel supply at the target pressure cannot be achieved.